Windows programs offer you a choice of printers, but sometimes the menu won't contain the printer you want. You can fix this by following a simple procedure which you should only need to carry out once for each Windows machine you use.
If the printer is asking you to load a tray, this normally means that it is out of paper. If you have filled all the printer trays and are still getting this message, it may mean that someone has been playing about with the control panel menus.
If the printer is complaining about a paper jam, open the printer cover and carefully remove the jammed paper. Sometimes you will have to open the back of the printer or remove the tray or the toner cartridge in order to remove the jam.
If the printer is asking you to replace a cartridge, it has run out of ink, and all you can do is email me. Note, though, that "order cartridge" means only that the printer is running low on ink and does not require any action.
For more printer messages and basic instructions on how to print, see my web page about printing. For difficulties with printing not covered here, the DAMTP page on what to do when printing goes wrong may be helpful.